Packet scheduling based on message length

ABSTRACT

A system using two algorithms for scheduling packets in a multi-hop network. The objective of the algorithms is to reduce end-to-end message (not packet) transmission delays. Both algorithms schedule packet transmissions based on the length of the original message to which the package belongs. The first algorithm is preemptive and is based on the shortest-message-first principle and the second is based on the shortest-remaining-transmit-time principle. We develop simulation models for analyzing the algorithms. The simulations show that when message sizes vary widely, these algorithms can significantly reduce average end-to-end message delays compared to the First-Come-First-Serve scheduling.

STATEMENT OF GOVERNMENT INTEREST

The invention described herein may be manufactured and used by or forthe Government for governmental purposes without the payment of anyroyalty thereon.

BACKGROUND OF THE INVENTION

The present invention relates generally to multi-hop networks and morespecifically the invention pertains to a system for packet schedulingbased on message length.

Network protocols, such as IP or ATM, transport data in packets. Thealgorithms used by these protocols, for routing, scheduling, flow andaccess control, are usually designed to satisfy performance measures atthe packet level (e.g., average packet delay). However, userapplications, such as file transfer (FTP), exchange data messages whichare not limited in size to that of a network protocol packet. Thisseparation between the application data and the way in which networksmanage that data often results in sub-optimal performance when measuredin terms of application layer messages. This paper describes packetscheduling algorithms that attempt to reduce end-to-end message delaysby taking into account message information in the scheduling of packetsacross the network.

Network layer packets are typically limited in size to hundreds orthousands of bits. As a result, data messages are fragmented intomultiple packets. These packets are then sent to the network layerprotocol for delivery across the network. As the packets traverse thenetwork they are queued at nodes along their way together with packetsbelonging to other messages. Typically, the network layer has noknowledge of the original message to which a packet belongs and servesthem on a First-Come-First-Serve (FCFS) basis.

Serving packets on a FCFS basis may be a reasonable strategy if one isonly concerned with packet delays. It is known that in a single node,average queuing delay is the same, regardless of scheduling policy, aslong as scheduling is not done on the basis of the packet length. Ifpackets are scheduled on the basis of their length, then it has beenshown that a scheduling policy that serves the shortest packet firstresults in minimum delays. However, from an end user point of view,message delays rather than packet delays is a more important performancemeasure. These messages can be as short as a few hundreds of bits for ashort e-mail, to Giga-bits for an image file. In this paper we areconcerned with the end-to-end delays experienced by these higher layermessages.

SUMMARY OF THE INVENTION

The present invention is a system that uses two algorithms forscheduling packets in a multi-hop network. The objective of thealgorithms is to reduce end-to-end message (not packet) transmissiondelays. Both algorithms schedule packet transmissions based on thelength of the original message to which the packet belongs. The firstalgorithm is based on the shortest-message-first principle and thesecond is based on the shortest-remaining-transmit-time principle.Simulations show that these algorithms can significantly reduce averageend-to-end message delays compared to First-Come-First-Serve scheduling.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chart of the average message delay in a single node system.

FIGS. 2 and 3 are charts of an example of AMP-PS and SRTT-PS scheduling.

FIG. 4 is an illustration of a single node system.

FIG. 5 is a chart of short message delay in a FCFS-PS system.

FIG. 6 is a chart of short message delay in a SRTT-PS system.

FIG. 7 is a chart of long message delay in a FCFS-PS system.

FIG. 8 is a chart of long message delay in a SRTT-PS system.

FIG. 9 is a chart of average message delay vs. load.

FIG. 10 charts average message delay vs. load for a single node system.

FIG. 11 is an illustration of a network using the present invention.

FIG. 12 is a chart of average delay for a system with two message sizes.

FIG. 13 is a chart of standard deviation for the delay of a system withtwo message sizes.

FIGS. 14 and 15 are charts of one cell message delay for the network ofFIG. 12.

FIG. 16 is a chart of message delay for the network of FIG. 12 withuniformly distributed message lengths.

FIG. 17 is the standard deviation of the delays of FIG. 16.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is a system for scheduling packets in a network.This new mechanism schedules the packets based on the length of theoriginal (application layer) message, with the objective of reducingend-to-end message delays.

In considering the scheduling of messages at a single node, it is clearthat when message sizes vary widely the scheduling of messages based ontheir size reduces average message delays considerably. As an example,in FIG. 1 we show the average queuing delay for a single node systemwith messages arriving randomly with exponential inter-arrival times.Half of the arriving messages are one cell in length and the other halfare 100 cells in length. Shown in the figure is the queuing delay fortwo scheduling algorithms. One algorithm serves the messages preemptivepriority over the long messages. As can be seen from the figure theaverage delay for the priority system is much lower than thecorresponding delays for the FCFS system.

In general, it is known that for a single server non-preemptive systemthe scheduling algorithm that minimizes average message delays givespriority to shorter messages over longer ones. In a preemptive systemthe scheduling algorithm that minimizes average message delays givespreemptive priority to the message with the shortest remainingtransmission time to completion.

While these scheduling algorithms were first studies in the context ofprocessor sharing systems, they are particularly applicable to datanetworks. In data networks message lengths are known in advance and canbe used to assign priority to packets. Further, since large messages arebroken down into small packets, or cells, an approximate form ofpreemption can be implemented by allowing messages to preempt oneanother only after the transmission of the current packet. So, a shortmessage priority algorithm can be implemented by giving packetsbelonging to shorter messages-priority cover those belonging to longerones. While this is not a pure form of preemptive priority scheduling,when packet sizes are much smaller than message sizes, it can achievemuch of the benefit of a pure preemptive algorithm without incurring theadded cost of preemption overhead.

In this idea of scheduling, messages based on the principle of givingpreemptive priority to the message with the shortest remainingtransmission-time was applied to an Ethernet LAN. There it was shownthat using this principle can significantly reduce message transmissiondelays. An exact analysis was developed for single node network wheremessages are scheduled based on the shortest remaining transmission timeprinciple. There, pure preemption was accomplished by fragmentingmessages into packets whenever preemption was needed and adding apacketization overhead every time a message was preempted.

In this paper we study the implementation and performance of packetscheduling algorithms in a multi-hop network that are based on the aboveprinciples. Implementing these algorithms in a single node network issimple because the state of the system is always known (i.e., the lengthand remaining transmission times of all messages). However, in amulti-hop network, where messages arrive at intermediate nodesfragmented into packets so that the complete message information is notavailable, the design of scheduling algorithms based on message lengthinformation is not as straightforward.

In addition, the performance evaluation of these scheduling algorithmsin a multi-hop network is complicated. In fact, even the computation ofaverage message delays in a simple FCFS network is generally notanalytically tractable: For FCFS scheduling some approximate models,such as Kleinrock's independence approximation are available. However,with the addition of a complicated service discipline obtaining accurateanalytical results becomes completely hopeless. We, therefore, resort tosimulation to evaluate the performance of the scheduling algorithmsdeveloped in this paper.

Below we describe the scheduling algorithms that we developed and howthey may be implemented in a multi-hop packet switched network. Then wediscuss simulation results of the algorithms in both a single nodenetwork and a simple multi-hop example network. Finally, we discuss ourdirections for future work and conclusions.

The scheduling algorithms we developed in this paper are based on theShortest-Message-Preempt (SMP) and Shortest Remaining Transmission Time(SRTT) principles. All of the algorithms that we describe are preemptivein the sense that a stream of packets belonging to another message.Therefore, these algorithms are preemptive at the message level, but notat the packet level. That is, no packet is interrupted in the middle ofits transmission.

These algorithms are designed to be implemented at every switch-in thenetwork. However, their implementation is independent from switch toswitch and requires no additional communication between the switches.Each switch implementing the algorithm is completely independent fromother switches in the network. The algorithms do not rely on anyinformation to be sent between the switches and, in fact, not allswitches need to implement the algorithm.

The algorithms are based on the SRTT and SMP principles, but they arenot a pure form of SRTT or SMP. This is due to the fact that pure SRTTor SMP would require every node in the network to have the fullinformation about each message. That is, every node would need to knowthe exact message to which every packet belongs and the state of thatmessage (i.e./ how much of it has already been transmitted). Since thisinformation is not available at the network level, these algorithmsapproximate the behavior of SRTT and SMP by including some limitedmessage information in the packet headers.

We discuss three algorithms. The first is simple First-Come-First-Serve(FCFS), which we use as the basis for comparison to the other twoalgorithms. The second algorithm is based on theShortest-Message-Preempt (SMP) principle and the last is based on theShortest-Remaining-Transmit-Time (SRTT) principle.

A. First-Come-First-Serve Packet Scheduling (FCFS-PS)

In FCFS-PS no effort is made to schedule the packets in a particularorder. Packets are served based on the order in which they arrive ateach node. Therefore, packets belonging to one message can beinterrupted by those belonging to another message simply based on timeof arrival. Essentially, FCFS-PS is the approach taken by packetswitches where no attempt is made to schedule packets based on messageinformation. We use the FCFS-PS algorithm as the basis for comparison ofthe other two algorithms.

It is very important to note that here FCFS-PS scheduling is not thesame as FCFS message scheduling for which MI/M and MIG/I queuing resultsapply. This is because in FCFS-PS packets and not messages are served ona FCFS basis. Therefore, in a multi-hop network messages naturallyinterrupt each other as packets belonging to different messages arriveon different input streams at overlapping time intervals.

B. Shortest Message Preempt Packet Scheduling (SMP-PS)

In pure SMP, shorter messages interrupt longer messages during theirtransmission and the longer messages resume their transmission once theshorter message is transmitted. Unlike pure SMP, SMP-PS only allowsinterruptions at the end of packet transmissions. Therefore if a packetbelonging to a short message arrives during the transmission of a packetbelonging to a longer message, it will not be transmitted until afterthat packet is transmitted. It will, however, be transmitted ahead ofthe rest of the packets belonging to the longer message.

In order to implement the SMP-PS algorithm, the network protocol mustknow the length of the message to which each packet belongs. This cansimply be done with the use of a length field in the packet header. Thislength field will contain the length of the original message to whichthe packet belongs. There are many ways in which to represent themessage length.

The simplest approach, and the one which we use in our simulation, is tolet the length field represent the number of packets contained in themessage (up to a maximum number of packets). This information is usuallyreadily available from the higher (e.g. transport) layer protocol. Thisapproach is particularly effective in a network where all packets are ofthe same length (e.g., ATM).

The SMP-PS algorithm can be implemented with a priority queue where thepriority of a packet is equal to the inverse of the length of themessage to which it belongs. The server serves packets from their queuein accordance with their priority and newly arrived packets are insertedinto the queue according to their priority.

For an example consider FIG. 2. On the top part of the figure thearrival of four messages is shown, according to the time in which themessages arrive. The first message to arrive (msg 1) contains 4 cells,the second message contains two cells, and the third and fourth messageseach contains three cells. For the purpose of the example, in each cellwe indicate the message number and the length of the message to whichthe cell belongs. On the bottom of the figure we show the order in whichcells are served. The first cell served is the first cell of message 1.When message 2 arrives, since it is shorter than message 1, the twocells belonging to message two are served. Following those, the firstcell of message 3, which is still shorter than message 1, is served.This cell is followed by the first cell of message 4. This is becausemessages 3 and 4 are of the same length and the first cell of message 4arrives before the second cell of message 3. With similar reasoning theremaining cells of messages 3 and 4 are served in round-robin order.When messages 3 and 4 are done the last 3 cells of message 1 are served.

For the purpose of comparison, we also show in FIG. 2 the servicesequence that would have resulted from FCFS-PS. As can be seen from thefigure, with FCFS-PS scheduling, message 1 would have been servedsooner, but messages 2, 3, and 4 would have all taken more time. In thisexample, the average message delay for SMP-PS is 6.75 cells and for theFCFS-PS it is 8 cells. Although this is only an example, it illustratesthe benefit of SMP-PS scheduling.

This example also illustrates one of the shortcomings of SMP-PSscheduling. Consider for instance the scheduling of messages 3 and 4. Inthis case the two messages are of the same length and arrive atoverlapping time intervals. Since the two are of the same length andhave the same priority, they are served in a round-robin order. Thisround-robin effect causes both messages to be unnecessarily delayed. Itis obvious that if we allowed message 3 to be served to completionfirst, the delay for serving message 3 would have been reduced withoutaffecting the message 4 delay.

Another related shortcoming of the SMP-PS algorithm is that messages canbe interrupted (by shorter ones) at any time during their transmission.So when a long message is being transmitted, and a shorter messagearrives, the shorter message interrupts the longer one even if thelonger message is almost completely transmitted. To illustrate -theabsurdity of this phenomenon consider two message of 100 and 99 cellseach. Suppose the 99 cell message arrives when the 100 cell message ison its previous to last cell. The 99 cell message would then interruptthe longer message and be transmitted completely, before thetransmission of the last cell of the 100 cell message can resume.Clearly this is an undesirable phenomenon. It is known that in a singlequeue, the best strategy would give priority to the message with theshortest remaining service time. With that strategy, the last cell ofthe longer message would have been transmitted before the 99 cellmessage. Also with that a strategy the round-robin effect discussed inthe previous paragraph would be eliminated. These ideas give rise to ournext strategy which is based on the shortest remaining transmission timeprinciple.

C. Shortest Remaining Transmission Time Packet Scheduling (SRTT-PS)

The obvious shortcoming of SMP-PS can be overcome by a simple variant ofSMP-PS which gives priority to packets based on the remainingtransmission time of the message to which they belong. In SRTT-PSscheduling, packets belonging to one message would have priority overthose belonging to another message only if the remaining transmissiontime of the message to which they belong is shorter than the remainingtransmission time of the other message. Again, as with SMP-PS,interruptions only occur at the end of packet transmissions. That is, nopacket transmission is interrupted.

In order to implement a SRTT-PS algorithm, each node must have thecomplete message state information for every: message in its buffer.This is a much more complicated task than what was required to implementSMP-PS. To implement SRTT-PS, not only must we tag each packet with itsmessage length, but we must also tag each packet with a messageidentifier that will allow all nodes in the network to track the stateof each message. Since this message identifier is only used for thepurpose of scheduling, it does not have to be truly unique. Therefore, asimple message identifier tag can be implemented using random numbers.The length of the tag must be sufficient so that the likelihood ofhaving two different messages with the same tag at a given node is low.However, even if two messages have the same tag the algorithm willcontinue to work by reverting to SMP-PS scheduling for those twomessages.

In addition, for the purpose of simplifying the implementation, eachpacket can also contain a sequence number which gives the order of thatpacket within the message. This sequence number is used to determine howmuch of the message has already been transmitted through the node. It isfor use by the scheduling algorithm only and is not the same as thetransport layer sequence number used for the reordering of the packetsystem.

The SRTT-PS algorithm can now be implemented at each of the nodes in thenetwork. The implementation of the algorithm is independent from node tonode. That is, scheduling at each node is based only on the remainingtransmission time of messages at that node. The algorithm does not takeinto account the state of the messages in the entire network. Using themessage identification number, the message length and the sequencenumber, the priority of packets belonging to a given message can be setas follows. At a given node's buffer, let Smin be the smallest sequencenumber of any of the remaining packets belonging to that message (i.e.,all packets with smaller sequence numbers have already been transmitted)and let L be the message length. This tells us the Smin-I packets ofthat message have been transmitted and L—Smin still remain to betransmitted (assuming that sequence numbers start with 0). Then theremaining transmit time associated with all of the packets belonging tothe message can now be set to L-Smin and the priority of these packetswill equal the inverse of the remaining transmit time. Note, again, thatthis calculation is based on the state of the message at a given nodeand not at the entire network.

For example consider FIG. 3. Shown in the figure is the same messagearrival sequence as that used in FIG. 2. The sequence in which cells areserved is indicated at the bottom of the figure. In each cell, withinthe service sequence, we indicate the message number followed by theremaining message transmit time. Notice that message 1, which arrivedfirst, receives services first. Message 2, which is of length 2 cells isserved next. After that, service resumes for message 1, which has aremaining service time of 3. This remaining service time is the same formessages 3 and 4, but since the message 1 cells arrived first they areserved first. After message 1 is served, message 3 is served. Noticeagain that message 3 is served to completion before we begin servingmessage 4. This is because as message 3 receives service the remainingtransmit time is less than that of message 4 and therefore message 3 isnot interrupted.

We see in this example how both the round-robin phenomenon and theinterruption of nearly transmitted long messages exhibited by the SMP-PSalgorithm is avoided with the use of the SRTT-PS algorithm. In thisexample, the average message transmit time is approximately 6.25 cells,a slight improvement over the SMP-PS algorithm.

The example of FIGS. 2 and 3 are useful for the purpose of illustratingthe algorithms and their relative advantages. In order to gain moreinsight into the performance of these algorithms we have to resort tosimulations. In the next section we start with a discussion ofsimulation results for a single node network and then show simulationresults for a network with a more complicated topology.

III. Performance analysis

We analyze the performance of these scheduling algorithms through theuse of simulation. All of the simulations presented in this paper weredeveloped using the Opnet simulation tool. We start with a discussion ofa single node system and then we describe the simulation for an examplemulti-hop network.

A. Single node system simulation

The algorithm developed in the previous section, although designed for amulti-hop network, are also applicable to a single node system. In [8]order to gain some intuitive understanding of these algorithms, we startwith the simulation of a single node system. In all of our simulationswe assume for simplicity that the network uses fixed size packets (orcells). In a more comprehensive discussion of message scheduling for asingle node satellite broadcast system is presented. Here we simplypresent the simulation results for the system of FIG. 4, where a singlesource, generating messages of various lengths with exponentialinter-arrival times, feeds a server with a buffer. The server, for thepurpose of this example, has a service rate of one cell per second.

We start with a simple source which randomly generates messages of twosizes. Half of the messages are short messages which are only one cellin length and the other half are long messages which are 100 cells inlength. Note that in this case, there is essentially no differencebetween the SRTT and the SMP scheduling algorithms because messagesarrive at a node all at once and hence the round-robin effect iseliminated. Therefore, here we only show the results for the SRTT case.This simple case of two message sizes may not be realistic, but isuseful for the purpose of illustrating the behavior of these algorithms.Also, it is somewhat representative of recent trends in network trafficthat is due to the use of client server applications where shortrequests are answered with long transmissions (e.g. download of a longfile).

Our source generates messages with exponential inter-arrival times. Forthe simulation results shown in FIGS. 5-8 we use a message arrival rateof 0.0167 messages per second (inter-arrival time of 60 seconds), whichis equivalent to an 85% load on the server. All of the figures show atotal system delay (queuing plus transmission) for complete messagesover the entire simulation time of 100,000 seconds. FIG. 5, shows thesimulated message delay for the short messages when using FCFS. This is,perhaps the most important figure in the sequence. What we see is theeffect of having short messages queued behind long messages. The averagedelay for a short (1 cell) message in the FCFS-PS system is 251 cells.In contrast FIG. 6 shows the equivalent delay when SRTT-PS is used.Since, with SRTT packets belonging to short messages get priority overlong messages, we see in FIG. 6 that short messages experience minimaldelay. The average short message delay for SRTT-PS is 1.31 cells (orseconds).

Despite this significant improvement in the delay for the short messageswhen using SRTT-PS, in FIGS. 7 and 8 we see that the long message delayis almost the same for both systems. This is due to the fact that eventhough short messages preempt the long ones, the overall load on thesystem that is due to short messages is relatively low and has minimalimpact on long message delays.

The results from FIGS. 5-8 were conducted for a system with a load of85%. In FIG. 9 we show the average message delay vs. the load, for awide range of load values, for both the short and the long messages. Ascan be seen from the figure, the average delay for the long messages isalmost the same under the SRTT and FCFS service disciplines. However,the short message delay is a much smaller under the SRTT scheduling.This results in an overall reduction in average message delay of nearlya factor of two. Clearly these results are very encouraging for theSRTT-PS algorithm. However, it is clear that the use of just two messagesizes in the simulations may not be sufficient to properly evaluate theperformance of the algorithms.

In order to obtain additional insight to the performance of thealgorithm, we simulated the single server system with a wider range ofmessage sizes. The simulation results shown in FIGS. 10 and 11 are for asystem with messages sizes uniformly distributed between 1 and 100. Thatis, each arriving message is of size between 1 and 100 cells with equalprobability for each size. In FIG. 10 we show the average delay vs. theload for all three service disciplines. As expected, the SRTT-PSalgorithm results in the smallest delays, followed by the SMP-PS and theFCFS-PS algorithm. What we see from FIG. 10 is that the difference inthe delay values is not as significant as in the two message sizesimulations.. This implies that the benefits of SRTT and SMP are mostnoticeable in a system with a wide variation in message sizes.

B. Multi-Hop network simulation

While the single node network simulation shows many of the benefits ofmessage based scheduling, it fails to capture some of the effects thatoccur in a multi-hop network. For example, in a single node networkmessages are typically assumed to arrive one at a time. However, in amulti-hop network messages arrive as packets; and different messages,traveling along different routes, can arrive at an intermediate node inoverlapping time intervals. Consequently, the affects of a schedulingalgorithm in a multi-hop network may not be the same as in a single nodesystem.

In the simulations we use the network of FIG. 11. In this network wehave 5 source nodes, all sending messages to the same destination. Eachof the source nodes generates one fifth of the total traffic in thenetwork. All of the links in the network have the same capacity, of onecell per second. As a result the bottleneck in the system is the linkjust before the destination node. Clearly, most of the queuing delays inthis network will occur at the bottleneck link. We chose this examplenetwork in order to examine the performance of the scheduling algorithm,at an intermediate network node, where all of the traffic is “in-route”traffic. This gives us the opportunity to examine the performance of thealgorithm where messages are arriving at a node fragmented into packets,at overlapping time intervals, rather than complete messages arrivingone at a time.

As we did with the single node system, our first simulation is for avery simple message length distribution, where each source generatesmessages of two sizes; short messages which are one cell each and longmessages which are 100 cells each. In FIG. 12 we show the averagemessage delay vs. the network load at the bottleneck link for all threescheduling algorithms for both the long (100 cells) and the short (1cell) messages. As expected, the average short message delay for bothSMP and SRTT were essentially the same and substantially smaller thanfor the FCFS algorithm. For the long message delay, the SMP and FCFSalgorithms performed nearly the same. The surprising was that the SRTTresulted in the smallest average long message delay. This is despite thefact that SRTT gives preemptive priority to the shorter messages. Thisrather surprising result can be attributed to the fact that the SRTTalgorithm eliminates that round-robin phenomenon that occurs in FCFS anSMP. While with FCFS and SMP messages that arrive in overlapping timeperiods are served in a round robin order, based on the arrival times ofthe cells belonging to those messages, in SRTT this round-robin effectis eliminated. Consequently, SRTT results in reduced message delays forboth the short and the long messages under all three schemes. As shownin the figure, for short messages the delay variation is almost entirelyeliminated with the SMP and SRTT schemes. While for long messages FCFSand SMP resulted in almost identical standard deviations and SRTTslightly reduced delay variations. This result is significant because ittells us that for short messages SMP and SRTT not only reduce queuingdelay but almost entirely eliminate any variations in delay.

In FIGS. 14-15, we plot a simulation trace of the end-to-end delay forthe short messages in the FCFS and SRTT algorithms. These plots show ashort time interval during the simulation of a system with an 85% loadon the bottleneck link. Since the delays for SMP were very similar toSRTT and are omitted here for brevity. Similarly, the plots of longmessage delays for all three algorithms were very similar and areomitted for brevity. In FIG. 14 we see the message delay for shortmessages in the FCFS system. As can be seen from the figure, shortmessages are often delayed for 100's of cells, while they are “stuck”behind long messages in the buffer. In contrast, in FIG. 15 we show theshort message delay for the SRTT system. Here we see that short messagestake somewhere between 2 and 6 cells (seconds) to get through thenetwork. This makes sense because the shortest route between a sourceand the destination is two hops.

Finally, in FIGS. 16 and 17, we plot results for a uniform messagelength distribution, where messages are uniformly distributed between 1and 100 cells. Here again, we see that the average message delay isminimized by the SRTT algorithm and the FCFS results in the largestaverage delays. However, we also see from FIG. 17 that the standarddeviation in delay (over all messages) is largest with SMP and smallestwith FCFS. Overall, the results that were obtained for the multi-hopnetwork are very similar to those obtained for a single node system.These results are encouraging because they tell us that a simpleimplementation of the SRTT or SMP algorithm can reduce end-to-endmessage delays significantly.

While the invention has been described in its presently preferredembodiment it is understood that the words which have been used arewords of description rather than words of limitation and that changeswithin the purview of the appended claims may be made without departingfrom the scope and spirit of the invention in its broader aspects.

What is claimed is:
 1. A process for scheduling network layer packetsbased upon application message length, said process comprising the stepsof: identifying message lengths for all messages awaiting scheduling ofthe transmission into a network to identify shortest messages; and afirst prioritizing step performed by prioritizing messages fortransmission by sending shortest messages first.
 2. A process, asdefined in claim 1, wherein the identifying step is performed by notingeach length field in each message packet header.
 3. A process as definedin claim 2, wherein said first prioritizing step is performed byestablishing a priority for a message packet equaling an inverse lengthof the length field in each message packet header.
 4. A process, asdefined in claim 3, in which the first prioritizing step furthercomprises using a server which serves message packets in accordance withtheir priority and in which new message packets are inserted into thepriority queue according to their priority.
 5. A process as defined inclaim 1, further comprises a second prioritizing step of prioritizingmessages in accordance with the remaining transmission time.
 6. Aprocess as defined in claim 5, wherein said second prioritizing stepcomprises giving all messages preemptive priority if they possess ashortest remaining transmission time.
 7. A process, as defined in claim4, further comprises a second prioritizing step of prioritizing messagesin accordance with a remaining transmission time.
 8. A process asdefined in claim 7, wherein said second prioritizing step comprisesgiving all messages preemptive priority if they possess a shortestremaining transmission time.
 9. A system for scheduling network layerpackets based upon application message length, said process comprising:a means for identifying message lengths for all messages awaitingscheduling of transmission into a network to identify shortest messages;and a first prioritizing means for prioritizing messages fortransmission by sending shortest messages first.
 10. A system, asdefined in claim 9, wherein the identifying means is performed by anetwork noting each length field in each message packet header.
 11. Asystem as defined in claim 10, wherein said first prioritizing means isperformed by a server establishing a priority queue for all messageswith a priority for a message packet equaling an inverse length of thelength field in each message packet header.
 12. A system, as defined inclaim 11, in which the first prioritizing means further comprises usinga server which serves message packets in accordance with their priorityand in which new message packets are inserted into the priority queueaccording to their priority.